A Send Queue (correct capitalization: sendQ).
The most common method of ensuring the pass of all appropriate data to the intended destination, usually implemented at application level. Especially utilized by the ircds ran in various IRC networks.
A typical scenario with a need for queueing (notice the spelling) would include an ever-growing data-file - in actuality, a stream being transferred at a varying transfer-rate.
Buffers, sendQs, packet-sizes and all somehow relate, although many of them often seem like complete gibberish to the end-user - with only few visible results, these being unwanted lag or netburps.